OLED, as a new type of display technology, has unique advantages such as self-illumination, wide viewing angle, low power consumption, high efficiency, thin, rich colors, fast response, extensive application temperature, low drive voltage, used to make flexible, bendable and transparent display panel and environmental friendliness, etc. Therefore, OLED technology can be applied to flat panel displays and new generation of lighting, or can be used as backlight of LCD.
OLED is a device made through spin-coating or depositing a layer of organic material between two metal electrodes. A classic three-layer OLED comprises a hole transport layer, a light emitting layer and an electron transport layer. The holes generating from the anode through the hole transport layer and the electrons generating from the cathode through the electron transport layer combine to form excitons in the light emitting layer, emitting light. By changing the material of the light emitting layer, the OLED can emit red light, green light and blue light. Therefore, stable, efficient organic light-emitting materials with pure colors play an important role in the application and promotion of OLEDs. Meanwhile, it is also very urgent for the application and promotion of large area of panel display in OLEDs.
Among three primary colors (red, blue, green), the red and green light materials have made great development although the performance of red and green OLEDs have been dramatically enhanced, which also meet the market demands of the panels, their efficiency and stability need to be improved. Therefore, a research focus is to solve the above problems from the material design and device structure. In the dye-doped OLED, the energy transfer efficiency of the host material to the dopant has a great influence on the efficiency and stability of the device. Frequently used host materials include mCP and 26DCzPPy and their derivatives, all containing nitrogen atoms. Materials containing hydrocarbons only have relatively high relative stability and are suitable for industrial applications and commercialization. There are also a series of commercial materials for the host material of the blue fluorescent dye doping device, of which, the mostly used one early are 9,10-diphenylanthracene (DPA), 9,10-bis (naphthalen-2-yl) anthracene (ADN) and 2-methyl-9,10-bis (naphthalen-2-yl) anthracene (MADN). Devices made of this type of compounds have ordinary efficiency, and due to its easy crystallization produced by symmetry of molecules, the thin film form is easy to change, which reduces the device stability, thus, it cannot be widely used in the OLED industry.
